Bicycles and motorcycles typically are built on a frame comprising metallic tubular members that are either welded together or joined using lugs or other connectors. The frame may include various other elements, such as for instance a head tube for holding the front fork and for allowing it to pivot and a seat tube for receiving a seat post, etc. Other systems and assemblies are attached to the frame, such as for instance suspension systems, braking assemblies, electrical systems, a motorcycle fuel tank, etc. Further, the frame provides rigidity, dissipates vibrations, and protects other systems in the event of a crash, etc.
Composite materials are also used in the construction of bicycle and motorcycle frames. Tubes are fabricated from fiber-reinforced resin materials and are joined together, typically using a connector element that is molded and bonded to the tubes that are being joined. By way of a few specific and non-limiting examples, cast aluminum or reinforced plastic shells may be used. Unfortunately, this assembly process is slow and expensive, requires additional tooling, and results in a relatively week connection since the connector element usually must be split to go over the tubes. Further, connecting tubes in this way produces a step in the resulting joint, which is aesthetically unpleasant.
In a different approach, an entire composite frame may be fabricated as a single part. This approach involves joining together tubular structural members, either by laying up several layers of an epoxy-containing carbon-fiber strip as described in U.S. Pat. No. 4,900,048, or by using a complex mold with appropriate internal pressurization bladders to form pre-preg blanks into the desired shape as described in U.S. Pat. No. 6,340,509. Unfortunately, the above-noted approaches are labor intensive, require complex and specialized tooling, and are unsuitable for some applications.
It would therefore be beneficial to overcome at least some of the above-mentioned limitations and disadvantages.